According to today's requirements, electric motors are often used with an add-on unit that is firmly connected to the electric motor. For example, in many cases it is necessary to equip the electric motor with a firmly connected gearbox unit in order to make it possible to provide the required torque while keeping a compact design. Often additional add-on units, such as encoder units or controller units, are also firmly connected to the electric motor. Together, the electric motor and the add-on unit form an assembly that itself represents a unit and that is manufactured, sold and also deployed as such.
A plurality of ways of connecting an electric motor and add-on unit are known from the state of the art. For example, it is common to screw, caulk or weld the housing of an add-on unit, for example, of a gearbox, to the electric motor. These types of connections are either expensive or lead to radial deformations of the connected components. Although it is true that there is no danger of deformation provided the electric motor and add-on unit are screwed together, this type of connection requires, however, a connection flange on both the electric motor and on the add-on unit, as a result of which the required construction volume is relatively large, particularly in the radial direction. The assembly proves to be extremely complex and is additionally very expensive particularly when the electric motor and add-on unit are screwed together. This is accounted for by the fact that the bore holes in the two flanges must be made with extreme precision and the screws that are used, as additional components, make the final product more expensive. Particularly in the case of small motors and micro motors, screwing the electric motor to an add-on unit often is ruled out due to the abovementioned reasons, particularly due to the increased construction volume.
Furthermore, bringing about a connection between the electric motor and the add-on unit by means of a snap-on connection is known from the state of the art. For example, a positive-locking connection between a gearbox housing part made of plastic and an adapter plate of an electric motor is known from DE 19729988 C1. There the ring gear of a planetary gear forms the gearbox housing part that is connected to the electric motor. The adapter plate that is connected to the electric motor can be slid into the ring gear in such a way that the cylindrical outer circumference of the adapter plate lies flatly on the inner circumference of the ring gear. The adapter plate furthermore comprises a plurality of latching lugs that are distributed along the circumference and that engage in corresponding latching openings of the ring gear. When the two components are inserted into each other, the ring gear, which is made of plastic, is expanded and does not return back into its undeformed state until the latching lugs have snapped into the latching openings.
The connection known from DE 19729988 C1 is therefore suitable only when one of the two components to be connected is produced from plastic and consequently has a lower level of stability than, for example, a metal component.
A further snap-on connection of an electric motor and add-on unit, said connection not being limited to the use of components made of plastic, is known from DE 102009032088 A1. Here a single-slotted radial elastic lock washer is used that sits both in a circumferential groove of an outer wall of the first component and also in a circumferential groove of an inner wall of the second component. The connection flanges of the electric motor and add-on unit must accordingly have different outer dimensions.